Slightly OT: A shopping mall in germany, where paying for the use of the toilet is voluntary (50Ct / use) makes on avg. ~300€/day, during christmas season up to 8000€/day [2]. If I would own a venue at a highly frequented place I'd rather request 50Ct from the user. ;)
[1] https://www.welt.de/regionales/koeln/article13794805/Nette-T... (german)
[2] http://waz.m.derwesten.de/dw/staedte/oberhausen/gladbecker-f... (german)